PLEASE HELP! turbo/throttl . problem 2006 Audi tt Quattro
 

I have recently bought a 2006 Audi TT Quattro 1.8 liter 6 speed standard. In the high RPM's when I shift after I let off the gas and push in the clutch the RPMs shoot to the roof but it only happens after 4000 rpms when I am just cruising it does not do that does anybody have any idea what the problem could be?